Accuvant approached browser security differently than earlier attempts, which have relied on comparisons of vulnerability counts, the time it takes a vendor to patch or pointing browsers toward known malware sites.

Instead, Accuvant created testing tools that allowed its researchers to investigate the browsers' -- and Windows' own, since it tested only on that OS -- anti-exploit mitigation technologies, and determine exactly what those technologies did or did not do.

Chrome, concluded Accuvant, was the most "secured" -- Ryan Smith, chief scientist in the group, made a point to use that term rather than "secure" -- browser in large part because of its sandbox, technology that isolates the browser and its processes from the rest of the operating system and machine.

Through sandboxing, Chrome ensures that exploit code which does make it onto a system either cannot, or can only in extreme circumstances, wriggle out of the browser itself.

Accuvant downplayed traditional comparison methods -- relying on vulnerability tallies, for instance -- as too variable by vendor, and said that anti-malware blocking was also worthless, noting, "The URL blacklisting services offered by all three browsers will stop fewer attacks than will go undetected."

"We like to think that we've advanced the state of the art in browser security comparison," said Accuvant's Smith.

"This is a better litmus than a shouting match," added Valasek, who pointed out that Accuvant has released not only its paper, but also the testing tools it built and the data those tools collected.

Accuvant's conclusion: Chrome was the most secured browser of the trio, with IE and Firefox in second and third place, respectively.

NSS Labs gave Accuvant credit for the research even as it claimed that the testing was flawed.

"They created some good tests, did some decent work," said Phatak. "It's a good first step, but it needs to be an evenhanded treatment. We think [the test methodology] skews the results in a way that biased the end results."

Phatak and Moy said that NSS Labs had "no contractual relationship with Mozilla" when asked whether it was fronting for the open-source firm.

Google did not reply to a request for comment on NSS Labs' charges. Mozilla declined to directly react to NSS Labs' contention that Firefox was shorted by the Accuvant tests, or comment on the claims that the report was one part of a multi-stage campaign against the company.

Instead, Mozilla repeated a statement it issued last week when Accuvant released its paper.

"Firefox includes a broad array of technologies to eliminate or reduce security threats," said Johnathan Nightingale, director of Firefox engineering, in that statement. "Sandboxing is a useful addition to that toolbox that we are investigating, but no technology is a silver bullet."

Accuvant's browser security report can be downloaded from the company's website (download PDF).